Carboxyl modified olefinic copolymer compositions

ABSTRACT

The invention relates to a novel low profile additive (LPA) for uncured polyester resins and the resultant molding compositions. The low profile additive is the reaction product of an ethylene/alphaolefin copolymer with a carboxylic acid or anhydride, to thereby form a non-thermoplastic carboxyl modified polyolefin. The novel LPA is a remarkably effective dimensional stabilizer and has displayed the ability to achieve net expansion in a cured polyester resin molding composition.

This is a division of application Ser. No. 000,606 filed Jan. 5, 1987,now U.S. Pat. No. 4,767,806.

BACKGROUND OF THE INVENTION

This invention relates to carboxyl modified olefinic copolymercompositions which are improved additives for unsaturated polyestercompositions. More specifically, the invention relates toethylene/alphaolefin copolymers which improve the shrinkage and surfacesmoothness characteristics of an unsaturated resin mixture.

Molding compositions formulated of curable or thermosetting unsaturatedpolyester resins have enjoyed widespead use, specifically for makingfiber reinforced thermoset plastics. Fiber reinforced moldingcompositions are specifically employed to provide prepreg mats, sheetmolding compounds (SMC), and bulk molding compounds (BMC) which arematerials commonly used for preparing reinforced cured shaped articlesby either injection molding or press molding. The molding compositionsare typically mixtures of the unsaturated polyester resins, fillers,fiber reinforcers, initiators, thermoplastic polymers and other minoradditives such as mold release agents, thickeners, and pigments.

A continuous problem area in the thermosetting polyester resin art hasbeen encountered in the curing step of the unsaturated polyester resincomposition. When cured in a condensation solution or dispersion of anunsaturated monomer solvent, such as styrene, the molded product has atendency to shrink and crack, as well as a propensity to have a dullsurface. The shrinkage problem is particularly acute when the curedresin has fiber reinforcement. In this case the shrinkage of the curingresin produces an imprint of the fiber on the surface of the moldedarticle with resulting detrimental effects to the surface smoothness ofthe formed article. In this regard, the use of low profile additives orthermoplastic polymers has been a significant contribution to thecommercialization of polyester molding compositions by improving thesurface effects and dimensional stability of the cured products.

Curing of the molding compositions (e.g., SMC and BMC) generally takesplace at elevated temperatures. Generally, the shrinkage reductioneffect of the low profile additive is attributed to the fact that thelow profile additive (LPA) or thermoplastic polymer becomes less solublein the resin at elevated temperatures, causing a partial phaseseparation. A two-phase mixture results with the curing polyester resinconstituting the continuous phase and the thermoplastic or low profileadditive constituting the distributed phase. The discontinuous phasethermoplastic polymer within the composite has been found to decreasethe amount of shrinkage that occurs upon curing of the composite. It isgenerally observed that the greater the thermoplastic polymer contentthe greater the shrinkage reduction effect of the thermoplastic resin orlow profile additive.

Many attempts have been made in the art to improve the surfacecharacteristics of unsaturated polyester resins. One is disclosed inU.S. Pat. No. 4,100,224. This patent proposes the use of thermoplasticpolymers, and specifically discusses a thermoplastic graft elastomerwhich is the reaction product of a styrene copolymer and monomers suchas styrene or acrylonitrile. Although this composition decreasesshrinkage, the reduction is marginal.

The use of ethylene/propylene copolymers and terpolymers in variousforms, in unsaturated polyester molding compositions, has beenrecognized, for example, in U.S. Pat. No. 4,100,224 discussed above andin U.S. Pat. Nos. 3,880,950; 4,258,143; 4,299,927. U.S. Pat. No.3,880,950 discusses the use of a microgel polymer in conjunction with athermoplastic polymer in a polyester resin composition. Either or bothof the microgel polymer or the thermoplastic polymer may containcarboxyl groups. The preferred microgel polymer includes acopolymerization product of alpha, beta unsaturated carboxylic acidswith at least one of styrene, methyl methacrylate and acrylonitrile inthe presence of polybutadiene or polyisoprene. The microgel polymer isdescribed as having 0.1-10% by weight carboxyl groups.

U.S. Pat. Nos. 4,258,143 and 4,299,927 disclose thermoplastic lowprofile additives of a carboxyl modified polyolefin. Specificallyexemplified are the homopolymers polyethylene, polypropylene andpolybutylene. Generally, a wide range of thermoplastic homo- andcopolymers are discussed including ethylene/alphaolefin copolymers. Thecopolymer and homopolymer compositions are described as having a meltviscosity of 100-40,000 at 175° C. The lowest percentage shrinkageobtained by the use of the polyolefin modifier disclosed was 2.88% ascompared to a 3.5% shrinkage in a control polyester without athermoplastic polymer modifier.

Although various thermoplastic resins have been proposed in the art, thesearch still continues for improved low profile additives. Therefore,even though low profile additives are generally known, and specifically,they are known for their reduction of shrinkage in curing compositions,there still remains considerable room for improvement in terms of bothshrinkage control and improvement in surface characteristics of thefinal molded article formed from molding compositions containing lowprofile additives.

SUMMARY OF THE INVENTION

Accordingly, an object of this invention is to provide improved lowprofile additives for use in unsaturated polyester molding compositionswhich will improve their ability to resist shrinkage. This invention isdirected to the discovery that non-thermoplastic polymers areparticularly well suited as low profile additives. Particularly inaccordance with this objective, it has been discovered that certaincarboxyl modified ethylene/alphaolefin/ (optionally) nonconjugated dienecopolymers and terpolymers are particularly well suited for use as lowprofile additives. It has been found that non-thermoplastic low profileadditives, in accordance with the invention, provide dramatic control ofcuring shrinkage which results in exceptionally smooth surfaces in amolded thermoset mixture. The non-thermoplastic carboxyl modifiedethylene/alpha olefin is suitably formed from a precursorethylene/alphaolefin as described in our U.S. Pat. No. 4,668,834, filedOct. 16, 1985, the disclosure of which is incorporated herein byreference. The ethylene/alphaolefin is suitably modified by a carboxylgroup in the presence of a free radical initiator. These particularcarboxyl modified ethylene/alphaolefin copolymers are not thermoplasticsand have been found to provide dramatic control of shrinkage and surfacesmoothness in the molded product. In fact, by the use ofnon-thermoplastic polymers it has been shown that net expansion of thecured molded part is possible when measured after cooling relative tothe cold mold cavity. Net expansion of the cooled molded part isextremely desirable and a considerable improvement in terms of thecommercial potential of unsaturated polyester molding compositions.Generally, the art has been limited to a mere decrease in the degree ofshrinkage.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Thus, the present invention relates to a novel low profile additive(LPA) for uncured polyester resins and their molding compositions. Thelow profile additive is the reaction product of an ethylene/alphaolefinwith carboxylic acids or anhydrides to form a non-thermoplastic carboxylmodified polyolefin. The novel LPA is a remarkably effective dimensionalstabilizer and has displayed the ability to obtain net expansion in acured polyester resin molding composition.

The non-thermoplastic polymers according to the invention are preferablyliquid at ambient conditions. The polymers are of relatively lowmolecular weights and desirably have low chain branching and lowcrystallinity. The polymerization of these non-thermoplastic polymerscan occur in the presence of hydrogen to lower polymer molecular weight.

The specific ethylene/alphaolefin copolymers to be modified by carboxylgroups as contemplated by the present invention comprise alphaolefinshaving a formula H₂ C═CHR wherein R is a hydrocarbon radical comprising1 to 10 carbon atoms. The copolymer optionally can contain anonconjugated polyene to form a terpolymer.

The alphaolefins, which may be employed in the practices of thisinvention, are preferably compounds of the formula CH₂ ═CHR wherein R isan alkyl radical containing from 1 to 10 carbon atoms. When R containsmore than 2 carbon atoms, such radical may be straight chain orbranched. Most preferred alphaolefins include propylene, 1-butene,1-pentene, 1-hexene, 3-methyl pentene, 1-heptene, 1-octene and 1-decene.

The polyenes which may be employed in the practice of this invention arenonconjugated. Illustrative nonconjugated polyenes are aliphatic dienessuch as 1,4-hexadiene, 1,5-hexadiene, 1,4-pentadiene,2-methyl-1,4-pentadiene, 3-methyl-1,4-hexadiene, 4-methyl-1,3-hexadiene,1,9-decadiene, exo and endo-dicyclopentadiene and the like; exo- andendo- alkenylnorbornenes, such as 5-propenyl-, 5-(buten-2-yl)-; and5-(2-methylbuten-[2']-yl)norbornene and the like;alkylalkenylnorbornenes, such as 5-methyl-6-propenylnorbornene and thelike; alkylidenenorbornenes, such as 5-methylene-, 5-ethylidene-, and5-isopropylidene-2-norbornene, vinylnorbornene, cyclohexenylnorborneneand the like; alkylnorbornadienes, such as methyl-, ethyl-, andpropylnorbornadiene and the like; and cyclodienes such as1,5-cyclooctadiene, 1,4-cyclooctadiene and the like.

The ethylene content of the copolymers of this invention is generally inthe range of between about 30 and 70%, and is preferably between about35 and 65%, and is most preferably between about 40 and 60% by weight.When present, nonconjugated polyene weight percent generally rangesbetween 0% and about 25%, is preferably between about 2 and 20%, and ismost preferably between about 4 and 17%. The remaining weight percent ofsuch copolymers (up to 100%) is comprised of alpha olefin.

The copolymers of this invention generally possess a number averagemolecular weight of between about 250 and 15,000, preferably betweenabout 1,000 and 12,000, most preferably between about 3,000 and 10,000.Consequently, such copolymers generally possess an intrinsic viscosity(as measured in tetralin at 135° C.) between about 0.025 and 0.55 dl/g,preferably between about 0.075 and about 0.45 dl/g, most preferablybetween about 0.2 and about 0.4 dl/g. However, these viscosity valuesare in no sense necessary for obtaining a non-thermoplastic copolymeraccording to the invention.

The non-thermoplastic copolymer of this invention, when of the typedescribed in our copending application referred to previously, ispreferably further characterized in that it may optionally possessvinylidene termination unsaturation. Thus, one end of such polymer willbe of the formula P-CR═CH₂ wherein R is as defined above (with respectto the alphaolefins which may be employed) and P represents the polymerchain. Preferably, at least about 50% of the copolymer chains possessvinylidene terminal unsaturation. More preferably, at least 60% of suchchains are vinylidene terminated, while most preferbly at least 75% ofsuch polymer chains exhibit vinylidene terminal groups. The percentageof vinylidene termination can be determined by spectrographic analysis.

Preparation of the copolymers described above is disclosed in U.S. Pat.Nos. 3,819,592; 3,896,094; and 3,896,096 and U.S. Pat. No. 4,668,834,all of which are incorporated by reference. The copolymers andterpolymers are further reacted with unsaturated or saturated carboxylicacids or anhydrides of aliphatic or aromatic type, which generallycontain three or more carbon atoms and one or more carboxylic acid oranhydride groups per molecule. Exemplary acids include maleic acids,mesaconic acid, chloromaleic acid, itaconic acid, citraconic acid,glutaric acid, adipic acid, sebacic acid, pimelic acid, orthophthalicacid, isophthalic acid, terephthalic acid, acrylic acid and methacrylicacid. Also suitable are anhydrides of the above acids, for example, theanhydrides derived from maleic, succinic, orthophthalic or other mono ordi-carboxylic acids. Also suitable, in certain instances, are highermolecular weight organic compounds containing carboxylic or dicarboxylicacid groups or the corresponding anhydrides thereof, for example,5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride or glycerol acetate bistrimellitate dianhydride or3,3',4,4'-benzophenone tetracarboxylic dianhydride, or pyromelliticdianhydride, among others.

The ethylene/alphaolefin copolymer is preferably reacted with thecarboxylic acid or anhydride with a free radical initiator. Suitablefree radical initiators which can be used for carrying out the carboxylmodification of the olefinic copolymer or terpolymer include organicperoxides with a half life of approximately 1/2 to 2 hours at atemperature of 70° to 160° C. Some examples of such peroxides aredi-t-butyl peroxide, dicumyl peroxide and benzoyl peroxide. Alsosuitable are peroxyesters such as t-butyl perbenzoate, t-butylperoxypivalate, 2,5-dimethylhexyl-2,5-di(perbenzoate), and so forth.This list is in no way considered exhaustive and any free radicalinitiator which possesses the required half life at the temperature ofthe reaction will be suitable for purposes of this invention. It wouldalso be possible to carry out the reaction by means of free radicalsgenerated by thermal or radiation sources such as ultraviolet light.

The carboxyl modified olefin copolymers in accordance with the inventioncan be prepared in any suitable reaction vessel, such as a resin kettleor pressure reactor which is charged with an olefinic copolymer,together with the carboxylic acid or anhydride, and a suitable freeradical initiator. The temperature of the reaction is normally withinthe range of 70° C. to 160° C. The reaction may be carried out in thepresence of an inert solvent such as cyclohexane, n-hexane, n-heptane,benzene, or xylene. Suitably inert solvents are employed if dilution ora lower viscosity of the mixture is desired. The dilution of the olefincopolymer is optional in that it is already in liquid form. However, fora more controlled reaction rate, dilution may be desirable. Furthermore,the use of lower temperatures than the above-mentioned range is alsooptional depending on the requirements of the reaction medium. Afterbeing charged with the reagents and optionally the inert solvent, thevessel is closed, flushed with nitrogen, and the temperature of thereactor is raised to the desired value.

The contents of the vessel are continuously stirred as the reactionproceeds to completion. Typically, the reaction is completed in aboutthree half lives of the initiator. The relative amount of the olefiniccopolymer or terpolymer, carboxylic anhydride or acid and free radicalinitiator which could be used in carrying out the reaction to form thecarboxyl modified polymer depend on factors such as the type andmolecular weight of the olefin polymer, the type of carboxylic compound,the type of free radical initiator, the temperature of the reaction, theamount of carboxyl functionality desired in the reaction product, andthe purity of the reagents. The determination of the reaction conditionsin light of these factors would be considered an obvious expedient toone of skill in the art in veiw of the general parameters outlined aboveand further discussed below.

When using the reaction product in a sheet molding compound or bulkmoulding compound to effect shrinkage control, it has been surprisinglyfound that shrinkage is minimized with an optimal molecular weight rangeof the carboxyl modified olefinic copolymers. This optimum molecularweight range of the modified copolymer is from about 5,000 to about14,000 number average molecular weight. The most suitable correspondingrange for the olefinic copolymer before it is modified in the carboxylicstep outlined above is about 3,000 to about 10,000 number averagemolecular weight. Therefore, this is considered a preferred molecularweight range of the polyolefin when employed to produce the carboxylmodified copolymer of the invention.

Surprisingly, it has also been found that the shrinkage control whichone obtains with the modified polyolefin copolymer, within the optimumrange stated above, is not dependent upon the particular molecularweight of the starting olefinic copolymer. Generally, as long as thenumber average molecular weight of the carboxyl modified polyolefincopolymer is within the range stated above, the molecular weight of theunmodified olefinic copolymer is not determinitive of the degree ofshrinkage control obtained. Therefore, it is feasible to prepare thedesired modified copolymer from many different starting polyolefincopolymers and to tailor the reaction conditions to produce a modifiedcopolymer within the above-stated optimum molecular weight range of themodified copolymer for best shrinkage control. This lends a great degreeof flexibility to production of the low profile additive, same beingdependent on the availability of reagents, relative costs of reagents,and reaction equipment and related costs.

Similarly, the optimum molecular weight range of the modified copolymerwith respect to the optimum surface smoothness corresponds to theoptimal molecular weight range recited above for optimum shrinkagecontrol. Additionally, at the high portion of the optimal molecularweight range of the modified polyolefin, the cured molding compositionwould still have excellent surface smoothness even though the shrinkagecontrol may have fallen off to less than that obtained in the middleportion of the optimal range.

With the above considerations in mind, the reaction conditions of theethylene/alphaolefin copolymer with the carboxylic reagent can best beillustrated generally with respect to a specific example. Specifically,it has been found that when using an ethylene-propylene copolymer whichhas the most preferred number average molecular weight of between about3,000 and 10,000, and using maleic anhydride as a carboxylic modifierand using di-t-butyl proxide as the free radical initiator, the typicalreagent amounts used are: 100 parts of copolymer, approx. 1 to 10 partsof maleic anhydride and approx. 0.01 to 1 part of initiator by weight.By operating under these conditions and concentrations, the reactionproducts obtained have contained approximately 0.1% to 10% by weight ofmaleic anhydride covalently bonded to the ethylene-propylene copolymer.This carboxylic weight percentage generally represents a preferred rangeof carboxylic groups on the olefinic copolymer when employed as a lowprofile additive pursuant to the present invention. The analysis for thecomposition of the product was carried out by conventional analyticaltechniques such as titration, and infrared spectroscopic analysis. Ofcourse, the above reaction conditions are exemplary only and othersuitable reagent concentrations, reaction times, and temperatures ofreaction would be readily ascertainable by one of skill in the artdepending upon the reagents employed and the products desired. Generalconsiderations as to the relative proportions of the reagents and thetime and the temprature of the reaction can be determined experimentallyto suit the particular materials on hand as well as the desired endproduct. Specific general considerations would be, for example, thatethylene-propylene terpolymers normally require less initiator thanethylene-propylene copolymers, or no initiator at all. Likewise, someolefinic copolymers and carboxyl compounds may be subject toautopolymerization with heating in the presence of certain freeradicals. In such cases, to minimize or avoid unwanted side reactions orcross linking, it may be desirable to reduce the temperature or time ofreaction, to reduce or omit the initiator, or even to add a crosslinking inhibitor such as dimethyl sulfoxide or dimethyl formamide.

Following the reaction of the copolymer to form the carboxyl modifiedcopolymer, subsequent processing of the modified copolymer productdepends upon the volatility of the possible byproducts and the degree ofproduct purity desired. If volatile byproducts are present, the reactoris cooled to approximately 25° C. to 60° C. and the contents transferredto an open container and placed in a vacuum oven at about 100° C. forapproximately 12 hours. This process removes volatile residues,solvents, etc. Alternatively, if it is known that the residues are not aproblem, the product may be used directly without vacuum processing in asheet molding or bulk molding compound recipe as described below.

If non-volatile residues are present, and it is desired to remove them,solvent extraction steps can be carried out. The solvent extraction canfollow the vacuum evaporation steps outlined above to effectivelyrecover purified modified copolymer. For example, when dicumyl peroxideis used as the initiator, the reaction products can be dissolved in asolvent such as hexane and partitioned, for example, by acetone. Theby-product residues will concentrate in the acetone layer and can bedecanted from the modified polyolefin which is in the hexane layer.

The modified copolymer reaction product low profile additive ispreferably placed in an unsaturated solvent monomer for its furtherreaction with a polyester for use as a low profile additive in a SMC orBMC molding composition. Suitable monomeric liquids are copolymerizablewith the unsaturated polyesters and develop therewith the crosslinkedthermoset polymer. The monomeric liquid should also have the ability todissolve the unsaturated polyester and the modified polyolefiniccopolymer in accordance with the invention. Suitable monomers wouldinclude styrene, alpha-methyl styrene, alpha-ethyl styrene, ringsubstituted styrenes, such as alkyl styrenes, e.g., ortho-, meta- andpara-alkyl styrenes, e.g., o-methyl styrene, p-ethyl styrene,meta-propyl styrene, 2,4-dimethyl styrene, 2,5-diethyl styrene, and thelike, halostyrenes, e.g., o-bromostyrene, p-chlorostyrene,2,4-dichlorostyrene, and the like. Alkyl esters of acrylic andmethacrylic acid, e.g., methyl, ethyl or butyl acrylate, methylmethacrylate, and the like, may also be employed. In addition, one mayalso use aliphatic vinyl esters such as vinyl acetate, vinyl butyrate,vinyl laurate, acrylonitrile, methacrylonitrile, vinyl chloride, and thelike. Further, acrylamide, methacrylamide and their derivatives may beemployed. Still further, one can make use of the allyl compounds such asdiallyl phthalate, allyl acetate, allyl methacrylate, diallyl carbonate,allyl lactate, allyl alpha-hydroxyisobutyrate, allyl trichlorosilane,allyl acrylate, diallyl malonate, diallyl oxalate, diallyl gluconate,diallyl methyl gluconate, diallyl adipate, diallyl sebacate, diallyltartronate, diallyl tartrate, diallyl mesaconate, diallyl citraconate,the diallyl ester of muconic acid, diallyl itaconate, diallylchlorophthalate, diallyl dichlorosilane, the diallyl ester ofendomethylenetetrahydrophthalic anhydride, triallyl tricarballylate,triallyltrimesate, triallyl aconitate, triallyl cyanurate, triallylcitrate, triallyl phosphate, trimethallyl phosphate, tetraallyl silane,tetraalyl silicate, hexallyl disiloxane and the like. Thesepolymerizable, ethylenically unsaturated monomeric cross-linking agentsmay be used singly or in combination with one another.

Other suitable monomers would be apparent to those skilled in the art.The preferred ethylenically unsaturated monomer would be styrene.

The modified polyolefin is then mixed with suitable polyesters in theformation of bulk or sheet molding compositions. The polyester resinsare generally condensation products of dicarboxylic acids and polyhyricalcohols. These are preferably unsaturated polyester resins. Theunsaturated polyester can be produced by any known method including thesolution method, the melting method, or the epoxy method.

Unsaturated dicarboxylic acids suitable in forming the preferredunsaturated polyesters include, but are not limited to, maleic acid,fumaric acid, itaconic acid, citraconic acid, chloromaleic acid,teraconic acid, glutaconic acid, mesaconic acid, and additional amountsof allylmalonic acid, propylidenemalonic acid, hydromuconic acid,succinic acid, carbocaprolactic acid, oxalic acid, malonic acid, citricacid, ethylmalonic acid, 4 amyl-2,5-heptadienedioic acid,3-hexyne-2,5-dionic acid, tetrahydromethalic acid, 3-carboxy sebacicacid, adipic acid, methylsuccinic acid, isophthalic acid, and the like.Of course, the acid anhydrides of any of the previously listed acids canbe used per se or in an admixture with the acid to produce theunsaturated polyesters in accordance with the invention. The reactionemploys alpha, beta ethylenically unsaturated polycarboxylic acids andtheir mixtures or other polymerizable carboxylic acids. Ifnon-alphabeta-polymerizable polycarboxylic acids are employed, they arenormally employed in conjunction with the α, β-ethylenically unsaturatedpolymerizable carboxylic acids in an amount up to 80%. The above list isnon-exhaustive, and is only meant to be illustrative. Other suitableacids or anhydrides would be readily apparent to those skilled in theart.

Suitable saturated alcohols would include dihydric or polyhydricalcohols such as 1,2 propane diol, dipropylene glycol, ethylene glycol,diethylene glycol, 1,3 butanedol, 1,4-butanediol, neopentyl glycol,triethylene glycol, tripropylene glycol, pentanediol, glycerol, and thelike and mixtures thereof.

The polyester resins employable in accordance with the invention are notlimited to those described above and any suitable polyester resin couldbe employable with the novel low profile additive. For example, thosepolyesters described in U.S. Pat. Nos. 3,718,714; 3,701,748, 3,880,950;and 4,096,107, the disclosures of which are incorporated by reference,are employable in accordance with the present invention.

The unsatuated polyesters are suitably dissolved in an unsaturatedmonomer such as those described as dissolving the low profile additive.The dissolution of the polyester in the solvent monomer is accompaniedby the dissolution of the low profile additive in the same or a misciblesolvent compatible with the crosslinking of the polyester. The mixturesolution formed from the polyester solution and the low profile additivesolution are such that they form a clear solution. The polyester and thelow profile additives are miscible or compatible with each other so asnot to form a dispersion. As stated in reference to the low profileadditive in accordance with the invention, styrene would be thepreferred monomer. However, any monomer could be employable which wouldsuitably be a crosslinking agent with the polyester during the moldingof the composition into a thermoset matrix. An advantage of theinvention low profile additive is that it is completely compatible withthe polyester resin in solution so as to form a clear solution. Thishomogeneous solution results in superior shrinkage reduction.

The polyester resin and the low profile additive are admixed in thepresence of a suitable initiator or curing agent. Suitable initiatorswould be free radical sources such as organic peroxide, organichydroperoxide, and azo compounds. Azo peroxide initiators are describedby, for example, Gallagher et al in "Organic Peroxides Review, PlasticsDesign Processing", July 1978, pages 38-42 and August, 1978, pages60-67, inclusive. The technologies disclosed in these two articles areincorporated by reference. Exemplary hydroperoxides include tert butylhydroperoxide, cumyl hydroperoxide,2,5-dimethyl-2,5-dihydroperoxyhexane, p-methanhydroperoxide andisopropylbenzenhydroproxide. Examples of azo compounds which can be usedin the composition of this invention include diazoaminobenzene,N,N'-dichloroazodicarboxylic acid amide, diethylazodicarboxylate,1-cyano-(tert-butylazo)cyclo hexanone and azobis(isobutyronitrile).Suitable conventional peroxides employable are benzoylperoxide,di-tert-butyl peroxide, cumene hydroperoxide, tert-butyl perbenzoate,parachlorobenzoyl peroxide, and the like. Generally, any suitableinitiator curing agent may be employed in accordance with the inventionsuch as those disclosed in U.S. Pat. Nos. 4,487,798 and 4,329,438, thesubstance of which are incorporated herein by reference. Theseinitiators are all of the type which function to generate free radicals.

In the practice of the invention the amount of carboxyl modifiedolefinic copolymer which may be used as a low profile additive cantypically vary, but is not limited to, between about 1% to about 10% byweight of the total filled reinforced BMC or SMC molding composition.The type of free radical initiator and the amount to be used will dependon many variables such as type of part which is molded, the type andamounts of polyester resin, and whether other ingredients such asfillers, fiber reinforcement and other additive ingredients are calledfor by a specific application.

For example, in addition to the polyester resin and the carboxylmodified olefinic copolymer additive, also employable are suitablefillers which are selected from granular fillers such as calciumcarbonate, calcium silicate, silica, calcined clay, chalk, talc,limestone, anhydrous calcium sulfate, barium sulfate, asbestos, glass,quartz, aluminum hydrate, aluminum oxide and antimony oxide.

Also, fibrous reinforcement agents can be used which are suitablyselected, for example, from the group comprising fibrous glass, metals,silicates, asbestos, cellulose, carbon, graphite, polyesters,polyacryls, polyamides, polyolefins, cotton, hemp, flax, wood, paper,and the like. The preferred fiber is glass. The fibers can be used informs such as mats, fabrics, threads, chopped fiber and the like.Usually the other ingredients of the SMC or BMC must be mixed first. Theinitial mixture is then spread upon a film backing which moves through aglass chopping machie where the fiber strands are deposited typically inone inch links. Subsequently, more paste and a cover film is applied andthe finished sheet is rolled up for storage until needed for molding.Other suitable additives are colorants or pigments such as titaniumdioxide, carbon black, phthalocyanine pigments and the like.

Suitable thickeners can also be employed in the SMC and BMC mixtures inaccordance with the invention, which include oxides and hydroxides ofthe metals of Group IIA of the periodic table, which include magnesium,calcium, strontium, barium and zinc. Preferred are magnesium and/orcalcium. These thickening agents promote the SMC or BMC to becomeessentially tack free and easy to handle, and increase the viscositythereof. Such high viscosity carries the glass fiber reinforcements tothe edge of the mold during the molding process, which is generally verydesirable to have a uniform and high strength product.

In suitable cases there may be a desire to inhibit the curing of the SMCor BMC which contains the low profile additive, in which case it wouldbe desirable to employ a polymerization inhibitor. The polymerizationinhibitor would retard the entire polymerization reaction and effectstabilization of the composition during any storage period prior tocuring. The effect of the inhibitor could effectively be negated by theaddition of more polymerization catalyst or initiator or by acceleratingthe reaction by other means such as heating or irradiation. Possibleinhibitors include phenols, monoalkyl phenols, polyalkyl phenols havinga plurality of the same or different substitutents, e.g, ethyl, propyl,butyl and higher alkyl radicals attached to their nuclei; hydroquinone,tertiary butyl hydroquinone, and the like. The amount of polymerizationinhibitor employed depends on the nature of the polyester resin as wellas the storage stability duration required.

Additional additives employed are mold lubricants and release agentssuch as zinc stearate, and ultraviolet light absorbers and stabilizerssuch as barium or cadmium soap, phosphates such as dimethylphosphate,alkyl phenols such as BHT, quinones, amines and the like.

An exemplary SMC molding composition and its constituents, in accordancewith the invention, is presented below in Table I.

                  TABLE I                                                         ______________________________________                                                               Parts by                                                                      Weight                                                 ______________________________________                                        Unsaturated polyester (60% solution in styrene)                                                        20.0                                                 Low profile additive (40% solution in styrene)                                                         12.0                                                 Initiator                0.5                                                  Particulate filler       56.6                                                 Mold release agent       0.6                                                  Fiber reinforcement      10.0                                                 Thickening agent         0.3                                                                           100.0                                                ______________________________________                                    

The SMC or BMC paste may incorporate any of the above describedadditives by additive mixing means found in the art. The mixing methodis not critical as compared to conventional mixing techniques employedfor conventional low profile additives and other additives into apolyester resin. This is due to the liquid nature and low viscosity ofthe low profile additives employed in according with the invention. Thevarious additives are easily dispersed and incorporated into the SMC orBMC paste by conventional rotary mixers, varius blenders or extruders orsimilar equipment. In mixing the SMC or BMC molding composition, caremust be taken so as to not overheat the mixture by shear or otherwise,due to the presence of the free radical initiator and the reactivemonomers.

The low profile additive is generally employed so as to constitute 1 to10% by weight of the total filled, reinforced SMC composition asspecifically exemplified in Table I. The amount of low profile additiveis preferably 4 to 6% by weight of the reinforced SMC.

Generally, the low profile additive is present in an amount ranging fromabout 5 to about 100 parts per 100 parts of the polyester resin.Preferably, about 30 to about 50 parts per 100 parts of polyester resinare employed.

In the subsequent molding operations of the SMC and BMC compositionsemploying the novel low profile additive of the invention, the moldingcomposition has handling characteristics which are comparable toconventional SMC and BMC compositions. Therefore, the novel moldingcompositions require no special handling requirements as compared toconventional low profile additive containing compositions. All theconventional operations which are performed on conventional SMC and BMCcompositions are equally applicable to SMC and BMC compositions asmodified by the novel low profile additive. The molding conditions aredetermined mainly by the properties of the polyester resin and theinitiator and by special requirements relating to the size and/or shapeof the particular part being formed.

In laboratory testing, small flat SMC plaques were molded by typicalmolding techniques and conditions as is exemplified in the specificexamples set forth below. These examples are provided to be merelyillustrative of the present invention, however, and are not meant to belimitative.

EXAMPLES 1 TO 3

Examples 1 to 3 show the effect of increasing carboxyl modification ofethylene-propylene copolymer on mold shrinkage and surface appearance ina sheet molding compound.

The copolymer of Example 1 contains no carboxyl functionality, and istherefore not an effective low profile additive. By contrast, thecarboxyl modified copolymers of Examples 2 and 3 are increasinglyeffective. The latter two modified copolymers were prepared by loadingtogether into a 600 ml. pressure reactor 100 g. of liquidethylene-propylene copolymer (average molecular weight 3200, ethylene topropylene ratio of 50:50 by weight, intrinsic viscosity 0.15 dl/g.,iodine number approximately 1), 1.0 g. of dicumyl peroxide, and from 1to 3 g. of maleic anhydride. The reactor was closed, flushed withnitrogen gas, and heated to 150°-170° C. for 2 hours with stirring. Thereactor was then cooled to room temperature (R.T.), opened, andapproximately 500 ml. of n-hexane added, and the contents were stirredto dissolve the polymer. Subsequently, the contents of the reactor werecombined with 1000 ml of acetone, stirred, and decanted. This acetonewash was repeated two more times. The hexane layer, containing thepolymer, was then placed under vacuum at 70° C. for approximately 6hours. The purified, devolatilized polymer, being now a carboxylmodified ethylene-propylene copolymer, was analyzed by titration forcarboxyl content, and dissolved in styrene monomer for use in sheetmolding compound. The ratio of copolymer to styrene was 40:60 by weight.The non-carboxyl modified copolymer (Example 1) was similarly dissolvedin styrene.

Model sheet molding compounds (omitting glass fiber) were prepared bystirring together at room temperature in a one quart Waring Blender: 75g. of polyester resin (Aropol Q-6585), 49 g of the polymer solution fromabove, 1.9 g. of t-butyl perbenzoate, 225 g. of calcium carbonate(Atomite), 5 g of zinc stearate and 1.9 g of magnesium hydroxide. Thehomogeneous paste was stored in a closed container for 3 days at roomtemperature, after which it was placed in an 8×8×1/8 inch mold and curedat approximately 280° F. for 20 minutes at a pressure of approximately350 lbs. per square inch. The mold was opened while hot, and the sampleplaque was removed. Mold and plaque were allowed to cool to roomtemperature, and their dimensions measured with a vernier caliper.

Table II shows the effect of increasing maleic anhydride (MA) level ofthe adduct on dimensional change and surface smoothness of the SMCplaques. Negative dimensional change indicates net shrinkage, andpositive change indicates expansion, of the room temperature plaquerelative to the room temperature mold.

                  TABLE II                                                        ______________________________________                                        Use of 3200 Molecular Weight E-P Copolymer in SMC                                                  Dimension Change,                                                                           Surface                                    Example No.                                                                            MA Level, % mils/inch     Smoothness                                 ______________________________________                                        1        0           -3.1          poor                                       2        0.7         +0.4          fair                                       3        1.6         +0.5          good                                       ______________________________________                                    

EXAMPLES 4 TO 8

These examples illustrate the optimum molecular weight range of carboxylmodified olefinic copolymer (adduct) in controlling SMC shrinkage andimproved surface smoothness. The modified copolymers of these examples,and the model sheet molding compounds, were prepared by procedures verysimilar to those outlined in the previous two examples, except that thestarting ethylene-propylene copolymer had an average molecular weight of4600, ethylene to propylene ratio of 49:51 by weight, and possessed atleast about 75% vinylidene terminal groups, and that the initiator wasdi-t-butyl peroxide, the reaction was carried out at 150° C. for 3hours, the acetone wash steps were omitted, and the test plaquedimensions were 6×6×1/4 inch. The variations in the molecular weight ofthe adduct were achieved by varying the level of peroxide.

In Table III, Examples 5, 6, and 7 fall within the optimum molecularweight range for best shrinkage control. Examples 4 and 8 are on the lowand high side, respectively, of this optimum range. The surfacesmoothness of Example 8, however, is still very good, even thoughshrinkage control is slightly less than optimal. This latter effect waspointed out in the foregoing discussion.

                  TABLE III                                                       ______________________________________                                                        Adduct     Dimensional                                        Example                                                                              Peroxide Molecular  Change   Surface                                   No.    Level*   Weight**   mils/inch                                                                              Smoothness                                ______________________________________                                        4      0        4,170   ***  -5.2     poor                                    5      0.07     5,490        -1.7     v. good                                 6      0.33     7,660        +0.1     v. good                                 7      0.50     9,070        +0.3     v. good                                 8      0.70     11,930       -0.3     v. good                                 ______________________________________                                         *Parts of dit-butyl peroxide per hundred parts of Ep copolymer, by weight     **Number average.                                                             ***Equivalent to 4600, unchanged from starting value, within limits of        experimental error.                                                      

EXAMPLES 9 AND 10

These two examples illustrate the use of two ethylenepropylenecopolymers of differing molecular weights to produce carboxyl modifiedadducts which have similar molecular weights. When incorporated into asheet molding compound, both adducts give essentially the same degree ofshrinkage control and surface improvement. In Example 9,ethylene-propylene copolymer was used having an average molecular weightof 4600, being the same copolymer that was described above in Examples 4to 8. In Example 10, ethylene-propylene copolymer was used having anaverge molecular weight of 3000, ethylene to propylene ratio of 58:42 byweight, and containing at least approximately 60% vinylidene terminationin the copolymer chains.

The reaction to produce carboxyl modified adduct from each copolymer wasdone in a 1-liter pressure reactor, with constant stirring at 150° C.for 3 hours. The amount of maleic anhydride used in each case was 6parts by weight, relative to 100 parts of copolymer. The initiator ineach example was di-t-butyl peroxide, but differing amounts were used,as shown in Table IV below, to obtain similar molecular weights (in the9000 to 10,000 range) in the final adducts. The general procedures forcarrying out the carboxylation and preparing the sheet molding compoundsof Example 9 and 10 were the same as for Example 4 through 8.

                  TABLE IV                                                        ______________________________________                                                                      Dimensional                                     Example                                                                              Initiator                                                                              Initial Adduct                                                                              Change***                                                                              Surface                                No.    Level*   MW**    MW**  Mils/Inch                                                                              Smoothness                             ______________________________________                                         9     0.5      4600     9,070                                                                              +0.3     v. good                                10     0.8      3000    10,290                                                                              +0.2     v. good                                ______________________________________                                         *Parts of dit-butyl peroxide per hundred parts of copolymer by weight.        **Number average molecular weight.                                            ***Measured on room temperature cured sheet molding compound sample           plaque, 6 × 6 × 1/4 inches, relative to mold cavity at room       temperature.                                                             

These two examples demonstrate a surprising feature of our invention,i.e., that considerable latitude can be allowed in the initial averagemolecular weight of the olefinic polymer, but when the conditions of thecarboxyl modification reaction are tailored so as to bring the averagemolecular weight of the adduct into the optimum range (from about 5000to about 14,000) then optimum performance in shrinkage and surfaceproperties is obtained. The specific tailored reaction conditions for aparticular starting polymer can be readily determined by firstempirically determining the molecular weight increase vs. initiatorlevel for two or three base points, thereby establishing a curve fromwhich the resulting adduct molecular weight for a given initiator levelcan be predicted with a good degree of certainty.

EXAMPLES 11 TO 14

These examples show the use of ethylene-propylene-nonconjugated polyeneterpolymer (EPDM, Ex. 11), and the use of a dicarboxylic anhydride (Ex.12) in the practice of the present invention. The use of a commerciallyavailable low profile additive (Ex. 13) is included for comparisonpurposes.

The terpolymer of Example 11 was made from the monomers ethylene andpropylene in the ratio of approximately 50:50 by weight, and includeddicyclopentadiene as the termonomer in an amount such that the iodinenumber of the polymer was approximately 19. This terpolymer had anaverage molecular weight of about 6500.

A 300 g. sample of the EPDM terpolymer was placed in a 1 liter pressurereactor with 21 g. of maleic anhydride, and stirred at 160° C. for 4hours. The reactor was cooled to 80° C., and 300 ml. of n-hexane wereadded with stirring. Two successive extractions with 1000 ml. of acetoneeach were carried out, and the product was placed in a vacuum oven at50° C. overnight.

Example 11 further demonstrates that the initiator can be omitted whenusing a fairly reactive polymer, such as EPDM, and the desired carboxylmodification is obtained merely by heating the reagents together asdescribed above.

In Example 12, the same ethylene-propylene copolymer was used asdescribed above in Examples 1 to 3, and the carboxyl modification wasdone by reacting this copolymer with5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride (trade name Epiclon B-4400) in the presence of di-t-butylperoxide at 165° C. for 3 hours. The ratios of copolymer to anhydride toperoxide were 150 to 16 to 3, respectively, by weight. The reactionproduct was purified by vacuum devolatilization at 125° C., and acetoneextraction.

The low profile additive of Example 13 was Neulon T, available fromUnion Carbide Corp., which is available as a solution containing about54% styrene. The active ingredient is a proprietary poly (vinyl acetate)mixture. Neulon T is included for purposes of comparison to the otherexamples herein. Neulon T is known in the sheet molding compoundindustry as an excellent low profile additive. Since Example 13 is adirect comparison of this additive to the compositions of the presentinvention, and uses the same SMC receipe and test conditions, it servesto demonstrate that the additives of the present invention, when used inthe preferred optimum range of the invention, are superior to Neulon Tin terms of SMC shrinkage control. Surface smoothness likewise, in themajority of examples, is comparable to or better than that obtained withNeulon T.

Example 14 is included for comparison to show the dimensional changewhich results when no low profile additive at al is used in the SMC. InExample 14, the same recipe and procedure as in Examples 1 to 3 wasused, except that the amount of polyester resin was increased relativeto the other ingredients to compensate for the fact that no low profileadditive was included. In this way the concentrations of filler,initiator, and other recipe components were kept constant in relation tothe other Examples shown herein, so that a valid and direct comparisonof shrinkage can be made.

The test plaque of Example 14 shrank 18.0 mils/inch, and the surfacecontained large cracks and pits. This example constitutes a control caseto which the relative performance of the other examples can be compared.

Model sheet molding compounds for Examples 11 to 14 were prepared by thesame procedure as in Examples 1 to 3. The SMC test plaque dimensionswere 8×8×1/8 inches.

                  TABLE V                                                         ______________________________________                                                 Polymer     Dimension Change                                                                            Surface                                    Example No.                                                                            Used        mils/inch     Smoothness                                 ______________________________________                                        11       EPDM/MA     +0.8          good                                       12       EP/EPICLON  +0.1          good                                       13       NEULON T    +0.1          good                                       14       None        -18.0         v. v. poor                                 ______________________________________                                    

Other embodiments of the present invention will be apparent to thoseskilled in the art from a consideration of this specification orpractice of the invention disclosed herein. It is intended that thespecification of this application and the examples be considered asexemplary with the true scope and spirit of the invention beingindicated by the following claims.

We claim:
 1. A non-thermoplastic carboxyl modified polyolefin copolymer comprising the reaction product ofa. an ethylene/alphaolefin copolymer having a number average molecular weight ranging from 250 to 15,000 with vinylidene termination unsaturation on at least 50% of the copolymer chains, wherein the alphaolefin has the formula H₂ C═CHR, wherein R is an alkyl radical having 1 to 10 carbon atoms, and b. an unsaturated carboxylic acid or anhydride containing three or more carbon atoms and at least one carboxyl group.
 2. The carboxyl modified polyolefin of claim 1, wherein the ethylene/alphaolefin copolymer further comprises a non-conjugated polyene to form a terpolymer.
 3. The carboxyl modified polyolefin of claim 1, wherein the ethylene/alphaolefin copolymer was an intrinsic viscosity of 0.025 to 0.55 dl/g.
 4. The carboxyl modified polyolefin of claim 1, wherein the ethylene content is in the range of 30% to 70% by weight.
 5. The carboxyl modified polyolefin of claim 2, wherein the terpolymer has an ethylene content of 30 to 70% by weight, the non-conjugated polyene content of 6 to 25% by weight, with the balance alphaolefin.
 6. The carboxyl modified polyolefin of claim 1, wherein the number average molecular weight of the ethylene/alphaolefin copolymer is between 3,000 and 10,000.
 7. The carboxyl modified polyolefin of claim 1, wherein the alphaolefin is propylene.
 8. The carboxyl modified polyolefin of claim 2 wherein the non-conjugated polyene is 5-ethylidene-2-norbornene, 1,4-hexadiene, or dicyclopentadiene.
 9. The carboxyl modified polyolefin of claim 1, wherein the anhydride is maleic.
 10. The carboxyl modified polyolefin of claim 1 wherein 0.1 to 10 weight percent of the polyolefin are carboxyl groups. 